Shape memory polymers and methods of use

ABSTRACT

The presently-disclosed subject matter includes a compound comprising a first monomer, which is allyl-functionalized and crosslinkable, and a second monomer, which is not crosslinkable. In some embodiments the compounds are photocrosslinkable, and in certain embodiments are photocrosslinkable by ultraviolet light. Also provided are shape memory vascular grafts comprised the of present compounds that can transition from a temporary shape to an original shape when heated above a melting temperature of the graft. Still further provided are methods for treating vascular conditions that utilize embodiments of the present grafts.

RELATED APPLICATIONS

This application claims priority from U.S. Provisional PatentApplication No. 61/840,449, filed Jun. 27, 2013, the entire disclosureof which is incorporated herein by this reference.

GOVERNMENT INTEREST

This invention was made with government support under Grant Number CBET1219573 awarded by the National Science Foundation. The government hascertain rights in the invention.

TECHNICAL FIELD

The presently-disclosed subject matter relates to shape memory polymers.In particular, the presently-disclosed subject matter relates tovascular grafts comprised of allyl-functionalized shape memory polymersas well as methods of treating vascular conditions using the same.

INTRODUCTION

Vascular conditions can often lead to severe complications or evendeath. Such vascular conditions include, but are not limited to,hemorrhages, aneurysms, occlusions, and ischemic tissue. Vascularconditions also present unique treatment challenges. This isparticularly so when treating vessels that are small or difficult toaccess. For instance, traditional surgical treatment techniques areinvasive to surrounding tissue and can be costly, can result in a highamount of pain, and can require a lengthy recovery.

In this regard, this regard, thermo-responsive shape memory polymers(SMPs) have drawn extensive interest in a wide range of applications,including biomedical, aerospace, self-healing, and textile applications.See, for example, Xue et al. Synthesis and characterization of elasticstar shaped-memory polymers as self-expandable drug-eluting stents. JMaterial Chemistry 2012: 22(15). Such SMPs can recover their originalshape after being programmed into a distinct temporary shape.Poly(ε-caprolactone) (PCL) is an exemplary biocompatible, biodegradablepolymer FDA-approved for specific biomedical applications that can bechemically modified and cross-linked to form SMPs. However, its meltingtemperature (Tm) of 45° C. to 60° C. is too high for physiologicalapplications (37° C.). Thus, SMPs such as PCL have limited clinicalcapabilities in the treatment of vascular and other conditions.Furthermore, the use of other SMPs for therapeutic purposes has beenhampered they require an additional methacrylate functionalization stepor a multistep monomer synthesis scheme.

Hence, there remains a need for compositions and methods for treatingvascular conditions that are relatively noninvasive, painless, andinexpensive. There also remains a need for SMPs that can be used forsuch applications and that have melting points that are suited forphysiological applications.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A to 1E include (FIG. 1A) a synthetic scheme of α-allylcarboxylate ε-caprolactone (ACCL), (FIG. 1B) ¹H-NMR spectrum of ACCL,(FIG. 1C) a synthetic scheme for an x % PCL-y % ACPCL SMP network, (FIG.1D) ¹H-NMR spectrum of a 96% PCL-04% ACPCL copolymer, and (FIG. 1E) agraph of ACCL:CL feed ratio versus actual x % PCL-y % ACPCL molarcomposition.

FIGS. 2A and 2B include (FIG. 2A) a synthetic scheme for 100%PCL-dimethacrylate control, and (FIG. 2B) ¹H-NMR spectra of 100% PCL(top) and 100% PCL-dimethacrylate (bottom).

FIG. 3 includes a graph showing the correlation between y % ACPCL andthermal properties of crosslinked SMP networks.

FIGS. 4A to 4C include stress-controlled thermomechanical cycling of(FIG. 4A) crosslinked 96% PCL-4% ACPCL, (FIG. 4A) crosslinked 89%PCL-11% ACPCL, and (FIG. 4C) 100% PCL-dimethacrylate SMP networks, whereSMP films were (1) heated above their T_(m) and programmed into anelongated shape by subjecting to tensile stress (0.004 MPa min⁻¹ to0.039 MPa), (2) cooled (2° C. min⁻¹ to 0° C.) to yield the maximumstrain, ε₁(N), (3) relieved of stress (0.004 MPa min⁻¹ to 0 MPa) toyield the temporary shape, ε_(u)(N), (4) heated (2° C. min⁻¹) aboveT_(m) yielded the original shape, ε_(p)(N).

FIGS. 5A to 5F include shape memory demonstrations for 88% PCL-12% ACPCLshowing a (FIG. 5A) tubular original shape that is (FIG. 5B) deformedinto a thread by heating at 50° C., applying strain, and fixing in anice bath, (FIG. 5C) heating at 37° C. to recover the original tubeshape, as well as (FIG. 5D) 94% PCL-06% ACPCL guitar shape (FIG. 5E)heated to 50° C., strained, contorted, and fixed at 4° C. before (FIG.5F) ultimate recovery of the original guitar shape at 48° C.

FIG. 6 includes a chart showing the covariance between physicochemicaland thermal, mechanical, and shape memory properties for aphotocrosslinked SMP library, wherein the degree of covariance betweenproperties is represented by the color and annotated values, indicatingthe nature of correlation between the variables (y %=y % ACPCL;Xg=X_(G); Mn=M_(n); Mw=M_(w); Tm=T_(m); H_(m)=ΔH_(m); Tc=T_(c); Etn=E′(37° C.); Snmax=ε_(max); Ssmax=σ_(max); Rr=R_(r)(N); Rf=R_(f)(N)).

FIG. 7 includes a graph showing the viability of HUVECs seeded directlyon polymer surfaces at specified time points (@=significantly differentfrom TCPS; *=significantly different from 1% agarose; and**=significantly different from 100% PCL and 1% agarose, or only to 100%PCL if located above the 1% agarose bar).

FIGS. 8A to 8E include confocal microscopy images of human coronaryartery endothelial cells (hCAECs) 3 days post-seeding on (FIG. 8A) TCPS,(FIG. 8B) 100% PCL, (FIG. 8C) 96% PCL-04% ACPCL, (FIG. 8D) 89% PCL-11%ACPCL, and (FIG. 8E) 88% PCL-12% ACPCL.

FIGS. 9A to 9C include images of a 88% PCL-12% ACPCL shape memoryarterial bypass graft (FIG. 9A) in its original tubular shape, (FIG. 9B)after being heated, deformed, and fixed into its temporary, thread-likeshape, and (FIG. 9C) after recovery of the original tubular shape at 37°C.

FIGS. 10A to 10E include schematics for a minimally-invasive bypassgrafting of (FIG. 10A) an occluded blood vessel (e.g. double carotidartery ligation), showing (FIG. 10B) implantation and suturing of theSMP in its thread-like geometry, (FIG. 10C) functionalization byembedding in collagen hydrogel with C16 and Ac-SDKP peptides, (FIG. 10D)recovery of the SMP's tubular original shape, and (FIG. 10E) bloodperfusing through the tube and functional biomolecules that inducesangiogenesis for regeneration and reperfusion of the occluded regionover time.

FIGS. 11A to 11C include confocal images from fluorescencemicroangiography showing the (FIG. 11A) “Polymer+Peptide,” (FIG. 11B)“Peptide Only,” and (FIG. 11C) “Untreated” groups.

FIGS. 12A to 12B include images of hematoxylin & eosin (H&E) stainingafter two weeks of in vivo grafting showing capillary connection betweenthe polymer tube and native artery.

FIG. 13 includes a fluorescence microscopy image showing CD31 stainingas a vascular endothelial cell and leukocyte marker in the“Polymer+Peptide” group after 2 weeks. Scale bar=200 μm.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

The details of one or more embodiments of the presently-disclosedsubject matter are set forth in this document. Modifications toembodiments described in this document, and other embodiments, will beevident to those of ordinary skill in the art after a study of theinformation provided in this document. The information provided in thisdocument, and particularly the specific details of the describedexemplary embodiments, is provided primarily for clearness ofunderstanding and no unnecessary limitations are to be understoodtherefrom. In case of conflict, the specification of this document,including definitions, will control.

The presently-disclosed subject matter includes compounds and methodsfor treating vascular conditions. In some embodiments thepresently-disclosed compounds include novel allyl-functionalized shapememory polymers (SMPs) that can be crosslinked via pendant allyl groups.In some embodiments the presently-disclosed materials, such as vasculargrafts, are comprised of the SMPs, and in certain embodiments includethermo-responsive SMPs that actuate at or near physiological temperature(e.g., about 37° C.). The present materials and grafts are advantageousbecause they can be relatively high in elastic recovery, easy tomanufacture and program, low cost, compatible with vasculature, tunable,and/or biodegradable. Thus, embodiments of the present materials thatpossess some or all of these features are advantageous for manufacturingsimple and minimally invasive implantable devices for various biomedicalapplications.

In this regard, the presently disclosed subject matter includescompounds that can form SMP materials. In some embodiments the compoundscomprise a first monomer that is allyl-functionalized and crosslinkableand a second monomer that is not crosslinkable. In specific embodimentsthe first monomer is photocrosslinkable. The methods for making thepresent compounds are not particularly limited, and in some embodimentsthe compounds are made via a process that includes ring-openingpolymerization.

The ratio of the first monomer to the second monomer is also notparticularly limited. In some embodiments the compound is comprised ofabout 1 mol %, 5 mol %, 10 mol %, 15 mol %, 20 mol %, 25 mol %, 30 mol%, 35 mol %, 40 mol %, 45 mol %, or 50 mol % of the first monomer. Inother embodiments the compound is comprised of about 1 mol % to about 50mol % of the first monomer, about 1 mol % to about 30 mol % of the firstmonomer, or about 1 mol % to about 15 mol % of the first monomer. Insuch embodiments the remainder of the polymer can be comprised of thesecond monomer.

In some embodiments the first monomer, the second monomer, or bothinclude an ester. The term “ester” as used herein is represented by aformula R₁OC(O)R₂ or R₁C(O)O R₂, wherein R₁ and R₂ can be independentlyselected from, but are not limited to, an optionally substituted alkyl,alkenyl, alkynyl, or the like. The term ester is inclusive of“polyester,” or compounds comprising two or more ester groups.

In some embodiments the first monomer that is allyl-functionalizedincludes an allyl carboxylate group. In such embodiments, the monomermay include a carboxylate group that is then functionalized with anallyl group, or the monomer may be functionalized with the carboxylateallyl group. The carboxylate allyl group described herein can berepresented by the following formula:

In some embodiments the first monomer, the second monomer, or bothε-caprolactone (CL) and/or derivatives thereof. For instance, the firstmonomer including ε-caprolactone can include an α-allyl carboxylateε-caprolactone (ACCL) monomer. In some embodiments the compounds arebased on polycaprolactone (PCL) because PCL has desirable properties forvascular applications, including biocompatibility, suitable rates ofbiodegradability, and mechanical compliance. Thus, in certainembodiments the compound includes a poly(ε-caprolactone)-co-(α-allylcarboxylate ε-caprolactone) copolymer (PCL-ACPCL), and some embodimentsof the present compounds can include the following formula:

wherein x and y are integers having no particular limitation.Embodiments of the present polymers can also be characterized as x %poly(ε-caprolactone)-co-y %(α-allyl carboxylate ε-caprolactone) (x %PCL-y % ACPCL) wherein x % and y % correspond to molar ratios and haveno particular limitation.

In some embodiments of the compound is a block copolymer. A “block”copolymer refers to a structure comprising one or more sub-combinationof constitutional or monomeric units. In some embodiments,constitutional units are derived via additional processes from one ormore polymerizable monomers. There is no limitation on the number ofblocks, and in each block the constitutional units may be disposed in apurely random, an alternating random, a regular alternating, a regularblock, or a random block configuration unless expressly stated to beotherwise.

As mentioned above, the present compounds can includeallyl-functionalized monomers that are crosslinkable. The terms“crosslinkable,” “crosslink,” and the like are used here to refer to anattachment of one portion of a polymer chain to a portion of the samepolymer chain or a portion of another polymer chain by chemical bondsthat join certain atom(s) of the polymer chain(s). Exemplary chemicalbonds that can form crosslinks include covalent bonds and hydrogen bondsas well as hydrophobic, hydrophilic, ionic or electrostaticinteractions. In some instances covalently-crosslinked SMP materialsexhibit superior shape memory properties and thermal stability whencompared to SMP materials crosslinked by non-covalent bonds.

Cross-linking can be effected naturally and artificially. For instance,in some embodiments the first monomer is photocrosslinkable, where theterm “photocrosslink” and the like is used herein to refer to crosslinksthat are formed upon being exposed to electromagnetic radiation, such asvisible light and/or ultraviolet radiation. In some embodimentsphotocrosslinks can be formed by exposure to ultraviolet light having awavelength of about 100 nm to about 300 nm. The terms “crosslink” andthe like as used herein can be inclusive of the terms “photocrosslink”and the like.

In some embodiments the allyl-functionalized monomer includes a pendantallyl-including group (e.g. carboxylate allyl group) that can crosslink.In some embodiments the allyl-including group can photocrosslink toanother allyl-including group of the same compound or another compound.

In some embodiments the present compounds can further comprise abioactive agent. The term “bioactive agent” is used herein to refer tocompounds or entities that alter, promote, speed, prolong, inhibit,activate, or otherwise affect biological or chemical events in a subject(e.g., a human). The manner in which the bioactive agent is incorporatedinto a compounds is not particularly limited. In some embodiment thebioactive agent can be incorporated (e.g., mixed with) the compound. Insome embodiments the bioactive agent can be covalently bound to anallyl-including group of the first monomer via thiol-ene clickchemistry.

Exemplary bioactive agents may include, but are not limited to,anti-cancer substances, antibiotics, immunosuppressants, anti-viralagents, enzyme inhibitors, neurotoxins, opioids, hypnotics,anti-histamines, lubricants, tranquilizers, anti-convulsants, musclerelaxants, anti-spasmodics and muscle contractants including channelblockers, growth factors, miotics and anti-cholinergics, anti-parasiteagents, anti-protozoal agents, and/or anti-fungal agents, modulators ofcell-extracellular matrix interactions including cell growth inhibitorsand anti-adhesion molecules, vasodilating agents, inhibitors of DNA,RNA, or protein synthesis, anti-hypertensives, analgesics,anti-pyretics, steroidal and non-steroidal anti-inflammatory agents,anti-angiogenic factors, angiogenic factors, anti-secretory factors,anticoagulants and/or antithrombotic agents, local anesthetics,ophthalmics, prostaglandins, cell response modifiers, cells, peptides,which as used herein includes polypeptides, viruses, and vaccines.

In some embodiments the present compounds are biocompatible. Indeed,certain embodiments the present compounds and grafts are morebiocompatible with endothelial cells (ECs) than 100% PCL, as indicatedby higher levels of long-term cell viability and healthy cellmorphologies. The term “biocompatible” as used herein is intended todescribe a characteristic of substances that do not typically induceundesirable or adverse side effects when administered in vivo. Forexample, biocompatible substances may not induce side effects such assignificant inflammation and/or acute rejection. It will be recognizedthat “biocompatibility” is a relative term, and some side effects can beexpected even for some substances that are biocompatible. In someembodiments, a biocompatible substance does not induce irreversible sideeffects, and in some embodiments a substance is biocompatible if it doesnot induce long term side effects. One test to determine substance is tomeasure whether cells die upon being exposed a material in vitro. Forinstance, a biocompatible compound or graft may cause less than about30%, 20%, 10%, or 5% cell death.

Additionally or alternatively, some embodiments of the present compoundsare biodegradable. The term “biodegradable” as used herein describes acharacteristic of substances that degrade under physiological conditionsto form a product that can be metabolized or excreted without damage tothe subject. In certain embodiments, the product is metabolized orexcreted without permanent damage to the subject. Biodegradablesubstances also include substances that are broken down within cells.Degradation may occur by hydrolysis, oxidation, enzymatic processes,phagocytosis, other processes, and combinations thereof. Degradationrates for substances can vary, and may be on the order of hours, days,weeks, months, or years, depending on the material.

Embodiments of the presently-disclosed compounds can further compriseadditional functional groups and/or monomers to impart desiredcharacteristics upon the compounds. The addition of functional groups ormonomers to the compounds can impart desired functionalities to thecompounds and/or affect the melting temperature of the compounds. Thus,certain functional groups or monomers can be incorporated into acompound in order to tune the thermomechanical characteristics of thecompounds.

The presently-disclosed subject matter also includes shape memorypolymer (SMP) materials comprised of any of the presently-disclosedcompounds. In some instances the materials are utilized to form grafts,such as vascular grafts for a blood vessel (e.g., vein, artery).Exemplary vascular grafts can include a plurality of crosslinkedpolymers, the polymers including a first monomer that isallyl-functionalized and crosslinkable and a second monomer that notcrosslinkable, and the graft can be capable of transforming between atemporary shape and an original shape.

The term “temporary shape” refers to a shape that has been given to amaterial by exerting a force on the material and/or exposing thematerial to certain temperatures (i.e., programming step). While thematerial can retain its temporary shape for any length of time, theshape is referred to as being temporary because the shape exists onlywhen external forces exerted on the material. Furthermore, in someembodiments the materials can lose their temporary shape when exposed toa temperature above a melting temperature of the material, as describedbelow.

The term “original shape” refers to a shape of the material when thepolymers of the material are in their native, unstrained state. Once amaterial is in its original shape, a material will generally retain theoriginal shape unless an external forces or the like is applied to thematerial. Some embodiments of materials revert to and/or retain anoriginal shape when exposed in a physically unstressed state to atemperature above a melting temperature of the material (i.e., recoverystep). Crosslinks between the plurality of polymers that comprise thematerials, either chemical or physical in nature, help preventirreversible, plastic deformation during programming and recovery steps.

There are no particular limitations on what shapes can be assumed by thematerial in its temporary shape or its original shape. In someembodiments temporary shape is selected from a thread, a sheet, tubularshape, a shape corresponding to a blood vessel, a vascular patch, avascular bypass graft, a vascular stent, and combinations thereof.Likewise, in some embodiments the original shape can be selected from athread, a sheet, tubular shape, a shape corresponding to a blood vessel,a vascular patch, a vascular bypass graft, a vascular stent, andcombinations thereof. As discussed further below, certain shapes can beadvantageous for certain therapeutic uses of the present materials.

Embodiments of the present materials can thus be categorized asthermomechanical SMPs, whereby the polymers can exhibit a transitionfrom a temporary shape to an original shape when transitioning aboveand/or below a melting temperature of the compounds. For instance, amaterial may initially have an original shape, and a temporary shape canbe induced by heating the material above its melting temperature whileexerting a force on the material that molds or bends the material into adesired temporary shape. The material can retain its temporary shape ifit is then cooled to a temperature below the melting point of thematerial while holding the material in the temporary shape, and thematerial can substantially retain this temporary shape so long as it iskept at a temperature below the melting temperature of the material.Subsequently, the material can revert to its original shape by heatingthe material to a temperature above its melting temperature.

The present compounds and materials comprising the present compounds caninclude wide range of melting temperatures. In some embodiments thecompounds and materials comprising the compounds include a meltingtemperature of about 20° C. to about 50° C., including meltingtemperatures of about 20° C., 25° C., 30° C., 35° C., 40° C., 45° C.,and 50° C. In some embodiments the compounds and materials comprise amelting temperature that is at or substantially near physiologicaltemperature (e.g., about 37° C.) so that the materials may experience aswitch-like shape transition when implanted into a subject. The presentmaterials can also include relatively high elastic recovery. In someembodiments the present materials include a strain recovery rate (Rr)and/or strain fixity rate (Rf) of 90% or more, and in some embodimentsRr and Rf can independently be about 91%, 92%, 93%, 94%, 95%, 96%, 97%,98%, or 99% or more. The present materials can also possess qualitiesthat make them similar to and therefore appropriate for use inconjunction with and/or as a replacement for blood vessels. Forinstance, some embodiments of materials have compliant and ductilequalities that are suitable for use with vasculature. Some embodimentscan also include elastic moduli of about 1.0 to about 200.0 MPa at 37°C., which can be suitable for certain vascular applications.

The shape memory properties of the present materials can be tuned bymodifying the present compounds. The melting temperature and otherproperties of the materials can be altered by modifying the compounds ina manner that affects the allyl groups of the allyl-functionalized firstmonomer. Without being bound by theory or mechanism, this is due to thefact that the allyl of a compound can affect the crystallinity andspacing of netpoints of the compound and any materials comprising thecompounds. The molar concentration of the first monomer and/or theconcentration and arrangement of allyl groups on the first monomer cantherefore offer efficient means for tuning the thermomechanical, shapememory, and biological functions of the present materials. In someinstances the properties of certain embodied materials can be furthertuned through alteration of the molecular weight or gel content of thematerials.

The present compounds and materials described herein therefore have thesuperior and unexpected advantage of having tunable properties, and insome instances can be tuned to have physiologically relevant meltingtemperatures. Methods for tuning the properties of the compounds andmaterials include, but are not limited to, varying the molarconcentration of the allyl-functionalized first monomer in the polymer,varying the concentration of allyl groups in the allyl-functionalizedfirst monomer, and varying the size and molecular weight of the firstmonomer, the second monomer, or other monomers in the polymers, orcombinations thereof. In certain embodiments can be tuned to mimic arange of soft tissues.

The presently-disclosed subject matter further includes method fortreating a vascular conditions. In some embodiments the method comprisesadministering a vascular graft in a temporary shape to a subject in needthereof, the graft comprising a plurality crosslinked polymers thatinclude a first monomer that is allyl-functionalized and crosslinkableand a second monomer that not crosslinkable. The embodied methodsfurther comprise a step of allowing the vascular graft to transform fromthe temporary shape to an original shape. The transformation from atemporary shape to an original shape can be initiated by heating thegraft above the melting point of the plurality of polymers, and in someembodiments the heating is done passively from heat that is emitted fromthe subject.

The step of administering the graft can include coupling the graft to ablood vessel of interest. As used herein, the term “couple” and the likerefers to the attachment of the graft to a blood vessel by any means. Insome instances coupling refers to wrapping a sheet-like graft around ablood vessel. In other instances coupling refers to suturing athread-like graft to a blood vessel. In yet other instances coupling canrefer to inserting a blood vessel through an opening of a tubular graft.Thus, the term “couple” broadly refers to a multitude of methods ofconfiguring a graft in relation to a blood vessel or other treatmenttarget.

The terms “treatment” or “treating” refer to the medical management of asubject with the intent to cure, ameliorate, stabilize, or prevent adisease, pathological condition. The term “condition” is inclusive ofdiseases, disorders, and the like. “Treatment” includes activetreatment, that is, treatment directed specifically toward theimprovement of a condition, and also includes causal treatment, that is,treatment directed toward removal of the cause of the associateddisease, pathological condition, or disorder. In addition, this termincludes palliative treatment, that is, treatment designed for therelief of symptoms rather than the curing of the disease, pathologicalcondition, or disorder; preventative treatment, that is, treatmentdirected to minimizing or partially or completely inhibiting thedevelopment of the associated disease, pathological condition, ordisorder; and supportive treatment, that is, treatment employed tosupplement another specific therapy directed toward the improvement ofthe associated disease, pathological condition, or disorder.

Furthermore, the terms “subject” or “subject in need thereof” refer to atarget of administration, which optionally displays symptoms related toa particular disease, pathological condition, disorder, or the like. Thesubject of the herein disclosed methods can be a vertebrate, such as amammal, a fish, a bird, a reptile, or an amphibian. Thus, the subject ofthe herein disclosed methods can be a human, non-human primate, horse,pig, rabbit, dog, sheep, goat, cow, cat, guinea pig or rodent. The termdoes not denote a particular age or sex. Thus, adult and newbornsubjects, as well as fetuses, whether male or female, are intended to becovered. A patient refers to a subject afflicted with a disease ordisorder. The term “subject” includes human and veterinary subjects.

Vascular conditions that can be treated by the present grafts include,but are not limited to, strokes, aneurisms, ischemic vessels,hemorrhages, occlusions, ruptured vessels, rupture-prone vessels,stenosis, atherosclerosis, peripheral artery disease, an arteriovenousfistula, or a combination thereof. Those of ordinary skill in the artupon reviewing this paper will appreciate other vascular conditions aswell as non-vascular conditions that can be treated with the presentmaterials.

The graft can be implanted in its temporary shape or its original shape.In the event that the graft is implanted in a temporary shape,embodiments of the treatment methods can further include, before theadministering step, a step of cooling the graft in a temporary shape toa temperature below the melting temperature.

The mechanical and thermal properties of the present grafts can be tunedwithin this system to more closely match that of the native bloodvessels. In some embodiments the present grafts can include anelasticity that is akin to that of a native artery. This biomimicry canallow the present grafts to achieve superior results when compared tovein grafts or other synthetic grafts. For example, veins are notdesigned for and do not perform well under sinusoidal flow conditionstypically experienced by arteries, and also do not comprise a musclelayer akin to that of arteries. Consequently, vein grafts, such assaphenous vein grafts, can experience atherosclerosis, intimalhyperplasia, thrombosis, and restenosis. Furthermore, the process ofgrafting and processing a vein can itself cause ischemic damage to thevein. On the other hand, by virtue being elastic and mimicking othermechanical properties of arteries, the present grafts can be utilized asarterial grafts with fewer or none of the negative side effectstypically experienced by vein grafts.

Additionally, surgical procedures for treating vascular conditions, suchas conventional bypass surgery, are typically highly-invasive, which canprolong patient recovery and hospitalization times and limit treatmentoptions for those with arterial occlusions. However, the embodiments ofthe present grafts can include a temporary shape that facilitates theprocedure and render it less invasive. For example, in some embodimentsgrafts can be programmed into a thin thread-like temporary shape thatpermits administration via small bore catheters and can permit formanipulation of the graft alongside an artery. Alternatively, exemplarygrafts can be tunneled along an artery via attachment to a tunnelingdevice. Those of ordinary skill will appreciate other temporary shapesand methods for administering the grafts that can reduce the invasivenature of procedures for treating vascular conditions.

In specific embodiments the grafts can be utilized for bypassprocedures. In some embodiments the graft includes an original shapethat is a stent, which often takes an elongated tubular form. The graftcan be coupled to the outside of a vein graft by wrapping or placing thegraft around vein graft. This configuration can improve the adaptationof the vein to the high pressure, high flow environment of the arterialcirculation. In such embodiments the graft can include a temporary shapeof a sheet, such that the graft can be administered by coupling (i.e.,wrapping) the sheet around the vein graft and subsequently allowing thegraft to transition to its original stent shape in order to support thevein graft.

Some embodiments of the present treatment methods also provide bypassprocedures that do not require transection of a native artery. Forinstance, the graft can include a temporary shape that is a thread shape(i.e., elongated thread) for easy insertion of the graft into thesubject as well as easy manipulation of the graft long the artery. Thegraft can then be coupled to the artery by ligating it to the arterywith sutures or the like, and subsequently the graft can transform toits original vascular bypass graft shape. Subsequently, capillaryingrowth can be achieved from the artery into the adjacent graft suchthat the occluded region section of the adjacent artery can beregenerated and reperfused over time. Additionally, in some embodimentsthe graft can include and/or can be administered in conjunction withbioactive agents (e.g., peptides, growth factors, etc.) that canfacilitate angiogenesis.

Treatment can also refer to the placing a graft within or on a bloodvessel that has ruptured or that is prone to rupture. The graft can theninclude an original shape of a blood vessel patch that closes andprotects the rupture or potential rupture.

The presently-disclosed compounds and grafts therefore present severaladvantages for methods of treating vascular conditions. First, thegrafts can include an original shape that provides for a custom-fitgraft that avoids flow-mediated thrombosis and hyperplasia. The abilityto customize the original shape of the graft also makes it suitable forunusual vasculature, such as branched arteries, as well as for treatingother non-vascular conditions. The ability to customize the temporaryshape also permits the present grafts to achieve robust and facilesurgical placement via minimally invasive techniques.

Once implanted, the present grafts can offer mechanical compliance thatwithstands blood vessel pulsation similar to an artery. Further still,embodiments of the present grafts can be biocompatible and, optionally,can exhibit biodegradable characteristics that are sufficiently slow topermit healing of the vasculature. The present grafts can also have aporosity that promotes microvascular growth to repair damaged vesseltissue. The present grafts can therefore provide treatment methods thatare easily implemented, cost effective, and less invasive to thesubject.

Additionally, presently-disclosed subject matter further includes a kitthat can include a material comprised of an embodiment of the presentcompounds, packaged together with a device useful for administration ofthe material. As will be recognized by those or ordinary skill in theart, the appropriate administration-aiding devices will depend on thetemporary shape of a graft and/or the desired administration site.

EXAMPLES

The presently-disclosed subject matter is further illustrated by thefollowing specific but non-limiting examples. The following examples mayinclude compilations of data that are representative of data gathered atvarious times during the course of development and experimentationrelated to the presently-disclosed subject matter.

Example 1

This example describes the synthesis and characterization of anexemplary x % PCL-y % ACPCL copolymer library. To prepare this copolymerlibrary, a novel α-allyl carboxylate ε-caprolactone (ACCL) monomer wasfirst synthesized in a single reaction by lithium diisopropyl amine(LDA)-mediated carbanion formation at the α-carbon of ε-caprolactone(CL) and subsequent addition of allyl chloroformate (FIG. 1A). Morespecifically, in a 250 mL round-bottom flask, distilled CL (13.9 mL, 125mmol) was added dropwise to LDA (125 mL of 2 M inTHF/n-heptane/ethylbenzene, 250 mmol) in anhydrous THF (200 mL) at −78°C. After 1 hour, the temperature was raised to −30° C. and allylchloroformate (13.3 mL, 125 mmol) was added dropwise. Thirty minuteslater, the temperature was raised to 0° C. and quenched with saturatedNH₄Cl (30 mL). The crude ACCL was diluted in H₂O (100 mL), extractedwith ethyl acetate (300 mL×3), dried with Na₂SO₄, filtered, evaporated,and purified by column chromatography using Silica Gel Premium Rf(Sorbent Technologies, Norcross, Ga.) with 10% ethyl acetate in hexanes.Yield: 58% (14.3 g, 72 mmol). ¹H-NMR confirmed formation of the desiredACCL product, as indicated by characteristic allyl (5.92 (G_(i)), 5.31(H_(ii)) and 4.63 (F_(ii)) ppm) and CL peaks (FIG. 1B).

Ring-opening (co)polymerization (ROP) of ACCL with CL using adiethylzinc catalyst and 1,6-hexanediol initiator generated a library ofnovel x % PCL-y % ACPCL (x and y: molar ratio) copolymers withy=4.16-14.50% as determined by the ratio of allylic CH protons (G_(i),δ=5.92 ppm) to CH₂ protons at the ε-carbon of PCL and ACPCL units(ε_(ii), δ=4.15 ppm) (FIGS. 1C and 1D, Table 1). To form these polymers,varying molar ratios of dried ACCL and CL (100 mmol total) wereintroduced to a pre-dried test tube containing 1,6-hexanediol (0.5mmol). The polymerization mixture was degassed with twofreeze-purge-thaw cycles, submerged in a 140° C. oil bath, and catalyzedwith dropwise addition of Zn(Et)₂ (1 mmol, 15 wt % in toluene) for 1hour. The solution was precipitated in cold diethyl ether and driedunder vacuum.

As a control, 100% PCL (Table 1, M_(n)=11300 Da, PDI=1.54) was similarlysynthesized (Table 1, M_(n)=11628 Da, PDI=1.41) by adding2-isocyanatoethyl methacrylate (0.22 g, 1.42 mmol) to 100% PCL (1.0 g,86.0 μmol) in anhydrous THF (20 mL) in a 100 mL round-bottom flask. Thereaction mixture was heated to 60° C. and catalyzed with dibutyltindilaurate (10 μL, 17 nmol) for 1 hour. The product was washed with 100%hexanes and 90% hexane/10% methanol, then dried under vacuum. Theterminal hydroxyl-to-methacrylate conversion rate, or degree ofmethacrylation (D_(M)), was calculated by summing the normalizedmethacrylate proton integrals from 6.12 (I_(6.12)) and 5.61 ppm(I_(5.61)) peaks for 100% PCL-dimethacrylate, and then dividing by thenormalized integral from the CH₂ protons adjacent to the terminalhydroxyls for unmodified 100% PCL at 3.66 ppm (I_(3.66,notfunc)). ThePCL exhibited a terminal hydroxyl-to-methacrylate conversion (D_(M)) of90.5% (FIG. 2).

Allylic compounds attained were lower than the ACCL:CL feed ratios dueto lower reactivity of the ACCL monomer (Table 1, FIG. 1E). Molecularweight (M_(n)=12-19 kDa, polydispersity index (PDI)=1.78-2.50) wascontrolled by the 1,6-hexanediol initiator:total monomer ratio but wasalso influenced by the feed ratio of the less reactive ACCL monomer. Thehigher PDIs and lower yields (22.6-56.6%) attained for these copolymersmay be due to transesterification reactions involving both the polyesterbackbone and pendant allyl carboxylates. There is an inverserelationship between thermal properties and allyl composition, possiblybecause ACPCL disrupts PCL crystallinity, thereby lowering the T_(m) andpercent crystallinity (X_(c)) (Table 1).

TABLE 1 Characterization of x%PCL-y%ACPCL copolymers y%ACPCL TheoreticalActual y y Yield Initiator: M_(n) M_(w) PDI T_(m) X_(c) Copolymer [%][%]^(a)) [%] Monomer [Da]^(b)) [Da]^(b)) [M_(w)/M_(n)]^(b)) [° C.][%]^(a)) 100%PCL 0 0 86.2 1:100 11300 17368 1.54 53.0 ± 0.2 56.6 ± 1.5100%PCL- 0 0 N/A N/A 11628 16417 1.41 50.7 ± 0.5 45.8 ± 1.9dimethacrylate 96%PCL-04%ACPCL 8.2 4.16 44.8 1:200 15060 26870 1.78 45.9± 0.3 41.6 ± 1.2 94%PCL-06%ACPCL 9.0 5.74 38.3 1:200 16546 39050 2.3647.1 ± 0.1 36.1 ± 0.5 89%PCL-11%ACPCL 16.2 10.58 39.8 1:200 13627 340492.50 39.1 ± 0.3 30.4 ± 0.7 88%PCL-12%ACPCL 17.2 11.66 22.6 1:315 1908736430 1.91 41.6 ± 0.2 31.1 ± 0.7 85%PCL-15%ACPCL 22.5 14.50 56.6 1:20012095 28931 2.39 32.5 ± 0.4 24.4 ± 0.9 ^(a))y%ACPCL was determined bythe ratio of the 5.90 ppm integral, I_(5.90), to the 4.15 ppm integral,I_(4.15): y%ACPCL = 2 × I_(5.90)/I_(4.15) × 100% I_(4.15):.;^(b))Molecular weight properties were determined by gel permeationchromatography against PMMA standards (Agilent Technologies, Inc., SantaClara, CA) using a Phenogel 10E3A column (Phenomenex Inc., Torrance, CA)in THF. ^(c))X_(c) = ΔH_(m)/ΔH_(m) ^(o) × 100%, where ΔH_(m) ^(o) =139.5 J/g, the enthalpy of fusion for 100% crystalline PCL.

Example 2

This Example describes the preparation and characterization ofcrosslinked x % PCL-y % ACPCL and 100% PCL-dimethacrylate SMP filmsusing the polymers synthesized in Example 1. A subset of x % PCL-y %ACPCL copolymers and the 100% PCL-dimethacrylate control werephotocrosslinked to create the shape memory effect and evaluated interms of gel content, thermal, mechanical, and shape memory properties.The crosslinked x % PCL-y % ACPCL and 100% PCL-dimethacrylate SMP filmsof uniform thickness (0.2-0.3 mm) were produced from a 10 wt % polymersolution containing 3 wt % 2,2-dimethoxy-2-phenylacetophenone via a thinfilm applicator (Precision Gage & Tool, Co., Dayton, Ohio) and 365 nmirradiation (4.89 J cm⁻², 18.1 mW cm⁻²) with a Novacure 2100 Spot CuringSystem (Exfo Photonic Solutions, Inc., Mississauga, Ontario, Canada).After drying, samples were incubated in DCM for 2 days to determine gelcontent. Thermal properties were measured on a TA Instruments (NewCastle, Del.) Q1000 differential scanning calorimeter. Mechanical andshape memory properties were determined using a TA Instruments Q2000dynamic mechanical analyzer in tensile mode.

It was desired to produce SMPs with T_(m)'s both slightly above andbelow 37° C. as surgical preferences for the onset of shape recoverydepend on the particular biomedical application. In order to be used forvarious vascular applications, it was also desired that the SMP libraryexhibits tunable mechanical properties, with sufficient compliance andextensibility. Moreover, complete and repeatable shape recovery with anon-off “switch-like” response to small temperature changes is soughtafter in order to tightly control shape memory behavior and preserveimplant integrity and function following shape programming and recovery.Gel content (X_(G)) relates to the percent crosslinking of the material,and in some SMP networks a minimum X_(G) of 10% to 30% is required toachieve the shape memory effect. After photocrosslinking (365 nm, 4.89 Jcm⁻², 18.1 mW cm⁻²), the X_(G) of x % PCL-y % ACPCL films were anaverage of 57.3±7.2% in comparison to 72.0±17.3% for the 100%PCL-dimethacrylate control (Table 2). Prior to crosslinking, the T_(m)of all materials besides 85% PCL-15% ACPCL were great than 37° C. (Table1). Crosslinking of the materials resulted in a T_(m) reduction to43.4-29.7° C. for y=4.16-14.50% copolymer films (Table 2) due to therestricted mobility of the crosslinked polymer chains. This reducedchain mobility also disrupted the alignment of chains after melting, asindicated by a reduction in the percent crystallinity (X_(c)) aftercrosslinking. There was a dependence of the thermal properties, exceptfor T_(g), on molar composition for the crosslinked polymers (FIG. 3),as amorphous ACPCL disrupted the crystallinity of PCL and lowered theT_(m), X_(c), crystallization temperature (T_(a)), and enthalpy ofcrystallization (ΔH_(C)). The X_(c) generated was similar to branchedPCL crosslinked films, indicating that switch-like shape recovery ispossible with these SMPs. Crosslinking produced a library of SMPs withswitching temperatures (i.e. T_(m)'s) near 37° C. and sufficient X_(c)for complete shape recovery and switch-like behavior in physiologicalapplications.

TABLE 2 Gel content and thermal properties of crosslinked x%PCL-y%ACPCLSMP films X_(G) T_(m) ΔH_(m) X_(c) T_(c) ΔH_(c) T_(g) Composition[%]^(a)) [° C.] [J/g] [%]^(b)) [° C.] [J/g] [° C.]100%PCL-dimethacrylate 72.0 ± 17.3 48.1 ± 0.4 48.2 ± 0.5 34.6 ± 0.4  19.5 ± 1.0 48.6 ± 0.4 −54.2 ± 3.0 96%PCL-04%ACPCL 63.0 ± 8.6 43.4 ±1.2 44.6 ± 3.2 32.0 ± 2.3   15.8 ± 0.9 43.2 ± 6.1 −56.9 ± 0.194%PCL-06%ACPCL 60.3 ± 21.3 37.9 ± 0.9 39.1 ± 5.3 28.0 ± 3.8    2.4 ±0.5 38.7 ± 4.8 −58.8 ± 4.9 89%PCL-11%ACPCL 49.0 ± 6.2 37.9 ± 0.7 38.7 ±1.6 27.7 ± 1.2  −2.1 ± 0.7 36.5 ± 0.8 −57.1 ± 1.5 88%PCL-12%ACPCL 64.1 ±3.1 33.4 ± 1.2 33.7 ± 1.1 24.2 ± 0.8  −8.7 ± 0.2 31.4 ± 2.2 −58.7 ± 2.285%PCL-15%ACPCL 50.3 ± 0.6 29.7 ± 0.2 28.3 ± 2.7 20.3 ± 1.9 −13.9 ± 0.817.2 ± 0.9 −57.5 ± 1.1 ^(a))X_(G) = m_(extracted)/m_(initial) × 100%,where m_(extracted) is the mass after incubating in dichloromethane for2 days and subsequently drying, while m_(initial) is the initial mass;^(b))X_(C) = ΔH_(m)/ΔH_(m) ^(o) × 100%, where ΔH_(m) ^(o) = 139.5 J/g,the enthalpy of fusion for 100% crystalline PCL.

Mechanical properties of the SMP test films were assessed isothermallyat 37° C. to determine suitability for vascular applications. Theelasticity was of the same order of magnitude or one lower than the 100%PCL-dimethacrylate control (Table 3, for y=4.16-14.50%: tensile modulusat 37° C. (E_(tn)′(37° C.))=55.0-2.2 Mpa) that may be considereddesirable compliance for vascular applications. The higher y % ACPCLcrosslinked copolymer films displayed an order of magnitude lowerE_(tn)′(37° C.) that more closely matches that of native arteries andwas primarily the result of these materials partially or fully meltingat 37° C. Stress-to-break, σ_(max), was between 3.3-0.12 MPa and most ofthe materials had good ductility at 37° C., with over 85%strain-to-break, s_(max), for every test film but 85% PCL-15% ACPCL(s_(max)=28%). These experiments demonstrate that the library ofcrosslinked SMPs has appropriate extensibility and compliance forvascular applications.

TABLE 3 Mechanical and shape memory properties of crosslinked SMP filmsE_(tn)′37° C. ε_(max) σ_(max) R_(r)(1) R_(r)(N) R_(f)(N) Composition[MPa]^(a)) [%]^(a)) [MPa]^(a)) [%]^(b)) [%]^(b)) [%]^(c)) 100%PCL-dimethacrylate 53.8 ± 36.7 199.5 ± 71.2 4.68 ± 0.3 99.7 ± 0.1 99.5 ±1.4 98.3 ± 1.5 96% PCL-04% ACPCL 55.0 ± 17.1   93.4 ± 135.5  3.3 ± 0.499.4 ± 0.8 99.4 ± 1.3 94.2 ± 1.2 94% PCL-06% ACPCL 3.05 ± 2.6  253.0 ±19.4 2.36 ± 0.9 93.7 ± 0.9 98.5 ± 0.6 98.7 ± 0.3 89% PCL-11% ACPCL 4.53± 3.4  131.4 ± 81.9 0.77 ± 0.6 97.4 ± 0.7 99.7 ± 0.7 99.8 ± 0.2 88%PCL-12% ACPCL 4.24 ± 1.1   84.5 ± 89.1 0.99 ± 0.6 99.9 ± 9.2 99.0 ± 6.298.8 ± 0.9 85% PCL-15% ACPCL 2.18 ± 0.1   28.1 ± 32.2 0.12 ± 0.1 60.1 ±0.6 86.9 ± 4.7 99.6 ± 0.2 ^(a))Mechanical properties determined by atensile test with a stress ramp of 0.1 MPa min⁻¹ at 37° C.; ^(b))Shapememory properties determined by stress-controlled thermomechanicalcycling.${R_{r}(N)} = {\frac{{ɛ_{1}(N)} - {ɛ_{p}(N)}}{{ɛ_{1}(N)} - {ɛ_{p}( {N - 1} )}} \times 100\%}$describes how well shape is recovered (ε_(p)(N)) in comparison to thebeginning of the N^(th) cycle (ε_(p)(N-1)) after deforming to maximumstrain ε₁(N).;$\;^{c)}{R_{f}(N)} = {\frac{ɛ_{u}(N)}{ɛ_{1}(N)} \times 100\%}$ definesthe ability to maintain programmed shape ε₁(N) after unloading of stressto yield the temporary shape ε_(u)(N).; ^(f))A 96% PCL-04% ACPCL testfilm with X_(G) = 36.7 ± 8.6% had R_(r)(1) = 99.9 ± 0.2, R_(r)(N) = 99.8± 0.4%, and R_(f)(N) = 99.8 ± 0.1%.

Example 3

This Examples describes the preparation of SMP shapes to evaluate shapememory properties by stress-controlled thermomechanical cycling (FIGS.4A to 4C). Closed-end polymer tubes (˜1.0-2.0 cm length, ˜0.90 mm inI.D., ˜1.0-1.6 mm O.D.) were prepared by dipping a polyvinyl alcohol(PVA)-coated 0.90 mm O.D. glass capillary in the polymer filmpreparatory solution and UV-crosslinking as above. Capillariescontaining the tubes were dried and immersed in deionized H₂O and 100%ethanol before manually pulling the tubes off the capillaries. The tubeswere washed with H₂O, dried, and the open side of the tube was closed bydipping it in polymer solution and UV crosslinking. A guitar shapecomprised of 94% PCL-06% ACPCL was prepared by first laser etching(Epilog Laser, Golden, Colo.) a 2 mm PDMS mold containing a CAD-designedguitar, then pouring the 94% PCL-06% ACPCL polymer solution into themold and UV crosslinking (365 nm, 26.1 J cm⁻², 290 mW cm⁻²) on a 48° C.hotplate.

Shape recovery after the first cycle, R_(r)(N), which indicated thequantitative ability of materials to recover their original shape (e.g.tubular shape), was over 98% for test films of every materialcomposition except for 85% PCL-15% ACPCL (R_(r)(N)=86.9±4.7%) (Table 3).Shape fixity (R_(f)) represents the ability of materials to be fixed ina temporary shape (e.g. thread-like shape) and was over 98% for selectfilms of every material composition (Table 3). Depiction of threeconsecutive thermomechanical cycles for 96% PCL-04% ACPCL and 89%PCL-11% ACPCL (FIGS. 4B and 4C) illustrated the repeatable nature ofshape programming and recovery for these SMPs. Shape memorydemonstrations further affirmed the utility of the materials inbiomedical applications (FIGS. 5A to 5F and FIGS. 9A to 9C), includingthe desired thread-to-tube transition for minimally-invasive catheter orlaparoscope deployment in arterial bypass grafting at 37° C. Mostcopolymers possessed exceptional, tightly-controllable shape memorycapabilities.

Example 4

This Example evaluated structure-function relationships to betterelucidate correlations of material properties (T_(m), ΔH_(m), T_(c),E_(tn)′(37° C.), σ_(max), ε_(max), R_(r)(N), R_(f)(N)) withphysicochemical properties (y % ACPCL, M_(n), M_(w), PDI, X_(G)).Briefly, a 13×10 matrix was constructed containing the mean values ofeach variable to be compared (13 variables) for each of the 10 polymerfilms (FIG. 6). Matrix values were standardized to their z-score formore apt comparison between variables, and a covariance matrix wascomputed and plotted using MATLAB (MathWorks Inc., Natick, Mass.).

Covariances (covs) closest to the absolute value of 1 indicate thestrongest correlations between variables, with positive and negativevalues indicating direct and inverse relations, respectively. Thermalproperties, E_(tn)′(37° C.), and σ_(max) correlate strongly with y %ACPCL (cov=−0.80-−0.94), indicating a dominant role of molar compositionon these properties. Without being bound by theory or mechanism, thisdominance of molar composition on certain material properties can beexplained by the fact that altering allyl content simultaneously changesboth the crystallinity and spacing of netpoints of the crosslinkednetworks. R_(r)(N) was also impacted by molar composition (cov=−0.60),although it is conceivable that programming parameters (e.g. fixationand deformation temperature, stress or strain rate) could be adjusted toimprove R_(r)(N) for higher y % ACPCL copolymers. M_(n) correlatedstrongly with ε_(max) (cov=0.78), indicating that M_(n) may be increasedto improve the extensibility of these SMPs. Further, X_(G) can beadjusted to increase R(N) (cov=−0.54) and ΔH_(m) (cov=−0.46). Thus,several material properties are affected by molar composition, and manycan be tuned via modulation of other physicochemical properties tocomprise PCL-ACPCL SMPs with certain thermal, mechanical, and shapememory properties.

Example 5

This Example describes vascular compatibility studies utilized to assessthe biocompatibility of the films. Human umbilical vein endothelialcells (HUVECs) were seeded on polymer films and their viability wasmeasured over the course of four days using the resazurin assay (FIG.7). To prevent cell attachment on tissue culture polystyrene (TCPS)underneath test films, wells were coated with 1% agarose solution.Agarose-coated wells were dried, washed with 100% ethanol, UVsterilized, and washed with MesoEndo Endothelial Cell Growth Media (CellApplications, Inc., San Diego, Calif.). Ethanol-leached, media-soakedpolymer disks (˜31 mm², ˜50 μm thick) were then placed on theagarose-coated wells, and Passage 5 red fluorescent protein-expressingHUVECs (P5 RFP-HUVECs) (470 cells mm⁻²) were seeded directly on the filmsurfaces, TCPS (positive control), and 1% agarose (negative control).After 1.5 hours, 150 μL of media was added.

Viability was assessed at 9, 35, and 91 hour time points via theresazurin assay. Briefly, resazurin (5 μM in MesoEndo) was added to eachwell, incubated for 4 hours at 37° C., and 560/590 nmexcitation/emission of the supernatant was read on an Infinite® M1000Pro plate reader (Tecan Group Ltd, San Jose, Calif.). Viable cell numberwas calculated based on a standard curve of RFP-HUVEC fluorescence onTCPS, and % cell viability was normalized to TCPS controls. All sampleswere tested in biological quadruplicates.

100% PCL (Sigma-Aldrich, M_(n)=70-90 kDa) is known to be biocompatibleand was therefore selected as a control film. Nine hours post-seeding,there was no statistically significant difference in HUVEC viablity ontest SMP films (60.0-65.2% relative to TCPS) compared to 100% PCL(59.4±4.9%). At later timepoints, HUVEC viability on all copolymer films(102.9-106.7% for 35 hours and 85.0-103.0% for 91 hours) was greaterthan that on 100% PCL (66.0±14.4% and 64.1±32.0%, respectively).

Additionally, cell morphology was evaluated by seeding P5 human coronaryartery endothelial cells (hCAECs) (Cell Applications, Inc., San Diego,Calif.) directly onto polymer disks. After 3 days of incubation on thedisks or TCPS controls, cells were fixed with 4% paraformaldehyde (15minutes), permeabilized with 0.5% Triton X-100 (10 min), and blockedwith 10% Bovine Serum Albumin (30 min). Cells were then incubated with 2μM Ethidium Homodimer-1 (10 min) and 50 μM Alexa Fluor® 488 Phalloidin(Molecular Probes, Eugene, Oreg.) (20 min). Cells on polymer surfaceswere imaged on a LSM 510 META Inverted Confocal Microscope (Carl Zeiss,LLC, Thormwood, N.Y.), while TCPS controls were imaged with a NikonEclipse Ti inverted fluorescence microscope (Nikon Instruments Inc.Melville, N.Y.). Images were post-processed and analyzed using ImageJsoftware (NIH, Bethesda, Md.). Confocal microscopy of hCAECs on allfilms after 3 days demonstrated trademark cobblestone morpology (FIGS.8A to 8E). Thus, the SMPs were compatible with vascular ECs and couldpotentially endothelialize when used as an arterial bypass graft.

Example 6

This Example describes an in vivo arterial bypass grafting procedureconducted in order to assess the therapeutic viability of the presentcompounds and grafts. A SMP tubular graft was utilized to provide aconduit for blood flow past an occluded region in a model of rat carotidartery ligation in vivo. The 89% PCL-11% ACPCL copolymer was chosen asthe tubular construct because it possessed shape memory properties(R_(f) and R_(r)>99%), a T_(m) close to body temperature (37.9° C.), andhigh EC biocompatibility after 91 hours (103.0%) (FIGS. 9A to 9C).

Immediately prior to surgery, closed-end SMP grafts (0.9 cm I.D., 1.2 cmO.D., 1.5 cm length) comprised of 89% PCL-11% ACPCL were UV sterilizedand collagen gels containing C16 and Ac-SDKP were prepared. SpragueDawley rats were subjected to a double ligature of the left commoncarotid artery as a model of complete blood cessation (FIG. 10A). Testgroups included “Polymer+Peptide”, “Peptide Only”, and “Untreated” testgroups. In the “Polymer+Peptide” group, SMP tubes with tow closed endswere placed over the entire occluded area immediately following theligations, each tube end was tied to the native artery by suturing, andthe construct and artery were embedded in the collagen gel containingpro-angiogenic C16 and anti-inflammatory Ac-SDKP peptides by cotton swabapplication (FIGS. 10A to 10E). In the “Peptide Only” group, only thepeptide-containing collagen gel was applied immediately following theligations. No polymer or peptides were applied in the “Untreated” group.All incisions were sutured closed using non-degradable sutures. Ratswere given buprenorphine 0.05 mg/kg SQ every 8-12 hours as needed forpain and monitored for two weeks.

Following the two week implantation, fluorescence microangiography wasperformed using 0.1 μm diameter FluoSpheres® Carboxylate-Modified RedFluorescent Microspheres (Life Technologies Corp., Carlsbad, Calif.) inheparinized saline (1:20 dilution) to assess areas of capillary growthand blood perfusion. Within 3 hours of the perfusion event, the beadswere observed using a LSM 510 META Inverted Confocal Microscope (CarlZeiss, LLC, Thormwood, N.Y.). Rat tissue around the polymer-arteryinterface was embedded in optical cutting temperature (OCT), frozen at−80° C. for 24 hours, and sectioned (5 μm sections) using a cryotome.

To identify vascular cells around the polymer-artery interface, frozensections were stained with mouse anti-rat phycoerythrin (PE)-conjugatedCD31 antibodies (clone TLD-3A12, BD Biosciences) as an endothelial andleukocyte cell marker, then counter-stained with Hoechst 33258 nuclearstain (Life Technologies, Inc.). The Nikon Eclipse Ti invertedfluorescence microscope (Nikon Instruments Inc. Melville, N.Y.) was usedto capture images of the IF-stained OCT sections.

After 2 weeks, the very strong fluorescent signal in the“Polymer+Peptide” group from detection of fluorescent beads usingfluorescence microangiography (FIG. 11A) indicating that blood wasflowing through the tubular construct. There is little to no visiblefluorescence in the other test groups (FIGS. 11B and 11C), signifyingnear-complete occlusion without this combination treatment. Observationof a purple/pink microvessel network from H&E staining (FIGS. 12A and12B), and fluorescence of CD31⁺ vascular cells (FIG. 13) for the“Polymer+Peptide” group illustrated anastomosis between the polymer tubeand native artery via capillary interconnectivity.

Without being bound by theory or mechanism, capillary formation arosefrom the pro-angiogenic, anti-inflammatory activities of C16 and Ac-SDKPpeptides distributed throughout the polymer-artery interface, providinga means for blood to be diverted into the polymer construct and returnto the native artery via a pressure gradient generated following thedirection of blood cessation. Thus, the tubular construct attached withthe native vasculature via capillary connection can provide anadditional conduit with the occluded artery, and can eliminate the needto perform transection of an artery during arterial bypass graftingprocedures.

It will be understood that various details of the presently disclosedsubject matter can be changed without departing from the scope of thesubject matter disclosed herein. Furthermore, the description providedherein is for the purpose of illustration only, and not for the purposeof limitation.

While the terms used herein are believed to be well understood by one ofordinary skill in the art, the definitions set forth herein are providedto facilitate explanation of the presently-disclosed subject matter.

Unless defined otherwise, all technical and scientific terms used hereinhave the same meaning as commonly understood by one of ordinary skill inthe art to which the presently-disclosed subject matter belongs.Although any methods, devices, and materials similar or equivalent tothose described herein can be used in the practice or testing of thepresently-disclosed subject matter, representative methods, devices, andmaterials are now described.

The terms “comprising”, “including,” and “having” are intended to beinclusive and mean that there may be additional elements other than thelisted elements.

Following long-standing patent law convention, the terms “a”, “an”, and“the” refer to “one or more” when used in this application, includingthe claims. Thus, for example, reference to “a polymer” includes aplurality of such polymers, and so forth.

Unless otherwise indicated, all numbers expressing quantities ofingredients, properties such as reaction conditions, and so forth usedin the specification and claims are to be understood as being modifiedin all instances by the term “about”. Accordingly, unless indicated tothe contrary, the numerical parameters set forth in this specificationand claims are approximations that can vary depending upon the desiredproperties sought to be obtained by the presently-disclosed subjectmatter.

As used herein, the term “about,” when referring to a value or to anamount of mass, weight, time, volume, concentration or percentage ismeant to encompass variations of in some embodiments ±50%, in someembodiments ±40%, in some embodiments ±30%, in some embodiments ±20%, insome embodiments ±10%, in some embodiments ±5%, in some embodiments ±1%,in some embodiments ±0.5%, and in some embodiments ±0.1% from thespecified amount, as such variations are appropriate to perform thedisclosed method.

As used herein, ranges can be expressed as from “about” one particularvalue, and/or to “about” another particular value. It is also understoodthat there are a number of values disclosed herein, and that each valueis also herein disclosed as “about” that particular value in addition tothe value itself. For example, if the value “10” is disclosed, then“about 10” is also disclosed. It is also understood that each unitbetween two particular units are also disclosed. For example, if 10 and15 are disclosed, then 11, 12, 13, and 14 are also disclosed.

Throughout this document, references are mentioned. All such referencesare incorporated herein by reference.

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What is claimed is:
 1. A vascular graft, comprising: a plurality ofcrosslinked polymers, the polymers including a first monomer that isallyl-functionalized and crosslinkable and a second monomer that is notcrosslinkable; wherein the crosslinked polymers include crosslinkscomprising covalent bonds between allyl groups of theallyl-functionalized first monomers; and wherein the graft is capable oftransforming between a temporary shape and an original shape.
 2. Thegraft of claim 1, wherein first monomer includes an allyl carboxylategroup.
 3. The graft of claim 1, wherein the first monomer, the secondmonomer, or both are an ester.
 4. The graft of claim 1, wherein thefirst monomer, the second monomer, or both include ε-caprolactone (CL).5. The graft of claim 1, wherein the plurality of crosslinked polymersinclude a poly(ε-caprolactone)-co-(α-allyl carboxylate ε-caprolactonepolymer.
 6. The graft of claim 1, wherein the plurality of crosslinkedpolymers include about 1 mol % to about 30 mol % of the first monomer.7. The graft of claim 1, wherein the plurality of crosslinked polymersinclude a melting temperature of about 20° C. to about 50° C.
 8. Thegraft of claim 7, wherein the graft is configured to transform from thetemporary shape to the original shape when heated above a meltingtemperature of the plurality of crosslinked polymers.
 9. The graft ofclaim 7, wherein the temporary shape is selected from a thread, a sheet,tubular shape, a shape corresponding to a blood vessel, a vascularpatch, a vascular bypass graft, a vascular stent, and combinationsthereof.
 10. The graft of claim 7, wherein the original shape isselected from a thread, a sheet, tubular shape, a shape corresponding toa blood vessel, a vascular patch, a vascular bypass graft, a vascularstent, and combinations thereof.
 11. The graft of claim 7, furthercomprising a bioactive agent.
 12. The graft of claim 7, wherein theplurality of crosslinked polymers are biodegradable, biocompatible, orboth.
 13. A method for treating a vascular condition, comprising:administering a vascular graft in a temporary shape to a subject in needthereof, the graft comprising a plurality crosslinked polymers thatinclude a first monomer that is allyl-functionalized and crosslinkableand a second monomer that is not crosslinkable wherein the crosslinkedpolymers include crosslinks comprising covalent bonds between allylgroups of the allyl-functionalized first monomers; and allowing thevascular graft to transform from the temporary shape to an originalshape.
 14. The method of claim 13, wherein the graft is configured totransform from the temporary shape to the original shape when heatedabove a melting temperature of the plurality of polymers.
 15. The methodof claim 14, further comprising, before the administering step, coolingthe graft in the temporary shape to a temperature below the meltingtemperature.
 16. The method of claim 13, wherein the temporary shape isselected from a thread, a sheet, tubular shape, a shape corresponding toa blood vessel, a vascular patch, a vascular bypass graft, a vascularstent, and combinations thereof.
 17. The method of claim 13, wherein thegraft in the original shape is selected from a thread, a sheet, tubularshape, a shape corresponding to a blood vessel, a vascular patch, avascular bypass graft, a vascular stent, and combinations thereof. 18.The method of claim 13, wherein: the graft in the temporary shapeincludes a thread shape; the graft in the original shape includes avascular bypass graft; and the administering step includes coupling thegraft along a section of a blood vessel.
 19. The method of claim 13,wherein: the graft in the original shape includes a vascular stent; andthe administering step includes coupling the graft around a section of ablood vessel.
 20. The method of claim 13, wherein the vascular conditionis selected from a stroke, an aneurism, an ischemic vessel, ahemorrhage, an occlusion, a ruptured vessel, a rupture-prone vessel,stenosis, arteriosclerosis, peripheral artery disease, an arteriovenousfistula, and combinations thereof.